I have been following the tutorials on the GIMP and found one on vignetting. The description of the technique is found here.
My starting point is the following color original.
Then I converted the Mode to black and white with a little contrast curve manipulation.
I RIP'd Ken Lee's Bronze quadtone colors from here.
Then I followed the vignette example in the tutorial to generate the following.
The image changes with each step and leads to something closer to what I first envisioned when I tripped the shutter on the wee-digi-snapper.
Next exercise? Dodging and burning an image using the increasingly powerful Linux and the GIMP!